Catalyst for manufacture of tetramethyllead



3,322,685 CATALYST FOR MANUFACTURE OF TETRAMETHYLLEAD Paul Kobetz andFrancis M. Beaird, Baton Rouge, La.,

assignors to Ethyl Corporation, New York, N.Y., a corporation ofVirginia No Drawing. Original application Aug. 31, 1962, Ser. No.220,881, new Patent No. 3,192,240, dated June 29, 1965. Divided and thisapplication Apr. 28, 1965, Ser. No. 451,636

12 (Ilaims. (Cl. 252-429) This application is a division of ourco-pending application Ser. No. 220,881, filed Aug. 31, 1962, now PatentNo. 3,192,240, entitled, Process for Manufacture of Tetramethyllead.

This invention relates to the manufacture of alkyllead compounds, Moreparticularly, the invention relates to a new and improved process forthe manufacture of a tetramethyllead product.

It is known that the tetraalkyllead compounds can be made by thereaction of an alkali metal lead alloy and an \alkyl halide,particularly, the monosodium lead alloy, NaPb and the correspondingalkyl chloride. This type of synthesis reaction has been employed formaking large amounts of tetraethyllead. The chemical reaction isentirely operative for other tetraalkylleads, and of recent period-sconsiderable interest has developed in the manufacture and use oftetramethyllead, which is an appreciably more volatile lead antiknockcompound.

In the case of tetramethyllead, the yields obtained are not as high asdesired. Thus yields of the order of 70 percent are reported, and undercarefully controlled laboratory conditions, yields of about 77-78percent can be obtained. Such results are achieved using, for example, ahydrocarbon aluminum compound as a catalyst and in the presence of asmall quantity of an inert hydrocarbon liquid. Such liquids, desirablyemployed in the proportions of about one-twenty-fift-h to one-fifth partby weight per part of alloy, serve apparently as adjuvants to thecatalyst and provide the above mentioned yields at moderate reactionconditions. Diificulty is frequently encountered, however, indischarging the product of a reaction, such reaction masses containinglarge proportions of subdivided lead metal released by the reaction andsodium chloride formed, as well as the tetramethyllead formed.

An object of the present invention is to provide a new and improvedprocess for making tetramethyllead. An even more particular object is toprovide a new process for making tetramethyllead in high and elficientyields. Another object is to provide an improvement in tetramethylleadmanufacture whereby high yields are obtained, and also the discharge ofa reaction mass is greatly expedited and the incidence of reactivecatalyst component residues in a reaction mass is greatly reduced. Anadditional object is to provide a new and novel cat-alyst system havinga plurality of at least two components and exhibiting unusual andunexpected properties and attributes.

It has now been discovered that tetramethyllead can be synthesized inthe presence of a new catalyst system, and that high yields and otherbenefits not heretofore available, can be realized. The process of theinvention comprises the reaction of sodium lead alloy and methylchloride in the presence of a catalytic amount of the catalyst system,which in all instances includes an aluminum component and an organiccompound having at least one glycol ether grouping therein. The aluminumcatalyst is usually a hydrocarbon aluminum compound, but also can befinely subdivided aluminum metal or 3,322,68 Patented May 30, 1967 analuminum trihalide such as the trichloride, tri-bromide, or triiodide.By hydrocarbon aluminum compound is meant those organometallic aluminumcompounds having at least one hydrocarbon radical per aluminum atom, theremaining bonds of the aluminum being satisfied by hydrogen, otherhydrocarbon radicals or by other radicals or elements Which are innocousor not detrimental to the reaction. As described more fully below, awide variety of hydrocarbon aluminum compounds are suitable, including,typically, trialkyl aluminum compounds and numerous others asillustrated herein.

The catalyst system or composition also includes, as stated, an organiccompound having at least one glycol ether grouping, this being the grouprepresented by the expression The terminal bonds of a single group aresatisfied by hydrocarbon radicals or additional glycol ether groups. Theforegoing attribute is found not only in diethers of glycols, but incertain other categories of compounds. Thus among the types of compoundseffective as a component of the catalyst system are the lower dialkylethers of lower polyethylene glycols, cyclic diethers, dialkoxy loweralkanes, and alkyl ethers of methyl tetrhydrofuran. Good results areobtained with catalyst systems following the above requirements, viz.,having the hydrocarbon aluminum compound plus only one organocompoundhaving the glycol ether grouping, but in certain preferred embodiments,a plurality of the latter components are provided and additionalbenefits are accrued which are highly valuable in certain environments.

Typical hydrocarbon aluminum compounds which are suitable includetrimethyl aluminum, triethyl aluminum, ethyl aluminum sesquichloride,diethyl aluminum chloride, ethyl aluminum dichloride, tri-n-propylaluminum, tri-n-butyl aluminum, triisobutyl aluminum diisobutyl aluminumhydride, tniphenyl aluminum, trioctyl aluminum, diethyl aluminumhydride, diethyl aluminum ethoxide, and others. Generally, then,aluminum compounds having at least one hydrocarbon radical having fromone to about ten carbon atoms are fully suitable for use. The simpleralkyl aluminum compounds, such as mentioned illustratively above, arepreferred, When desired, the hydrocarbon aluminum catalyst component canbe generated in situ, as, for example, by the reaction of an aluminumtrihalide with a hydrocarbon compound of another metal. Thus, thereaction of aluminum trichloride and tetraethyllead will generatehydrocarbon aluminum moieties operative at this catalyst component.

The lower dihydrocarbon ethers of the lower polyethylene glycols are onetype of co-catalysts and are similarly not restricted to isolatedspecimens. The term dihydrocarbon includes both those diethers havingtwo identical hydrocarbon groups, and also those having dissimilarhydrocarbon groups, as, for example, the methyl ethyl ether ofdiethylene glycol. By lower polyethylene glycol is meant those compoundshaving in series up to about six or seven glycol groups, is.

wherein n is up to about 7. Generally it is preferred to employ thosemembers of this group having up to and including four such groups ormoieties, the others of diethylene glycol being especially preferred.The hydrocarbon radicals of these materials can be aryl, cycloalkyl,alkaryl, aralkyl, or similar alkyl groups. Simple alkyl groups of up toten carbon atoms are preferred, the normal alkyl groups of one to fourcarbons being especially preferred.

In carrying out the process, by a batch or cyclic technique, a reactionzone is charged with subdivided solid alloy, usually the monosodium leadalloy, although some variation from this is permissible, and then theco-catalyst system is charged. Various modes of charging can beemployed, and for particular catalyst systems, there can be minorbenefits associated with a particular mode. Thus, effective modesinclude adding separately the aluminum catalyst component and theco-catalyst or synergist portion, or pre-mixing these components, oradding one or both of the components in several increments separated byshort time intervals,

Frequently, the initial charge also includes an inert liquidhydrocarbon, in limited proportions. Usually, suitable proportions arefrom about one-twenty-fifth to about one-fifth of the alloy by weight.The hydrocarbon is particularly beneficial according to prior processesusing only a hydrocarbon aluminum catalyst, as in such instances, thehydrocarbon results in a greater effectiveness of single catalystcomponents. In the present invention, the hydrocarbon is usuallyoptional but generally beneficial. The hydrocarbon promotes thestability of the tetramethyllead product after recovery from thereaction mass. A wide choice is available for selection of an inertliquid hydrocarbon, commercial toluene being a particularly suitable'materal. As already stated, the use of the hydrocarbon is optional, andgood results are obtained without such a material.

After the above described charge, the reactor is sealed except fornecessary venting connections. The temperature is raised to, usually, atleast 65 C. or above, while the system is agitated, and methyl chlorideis charged. The methyl chloride in some cases is charged all at onetime, and in other cases is fed in over a deliberate finite period. Thetotal methyl chloride is provided in proportions of at least onestoichiometric re quirement or theory, and usually, a substantial excessis used. It will be understood that this refers to the total quantityfed during batch operations. During portions of such cyclic operations,only minor quantities of methyl chloride may be present, when the feedis spread out over a finite period.

The materials thus charged together are then reacted at temperaturesaveraging from about 85 to 110 C. Agitation is provided throughout thereaction period, as the reacting system includes solids and volatileliquids. The reaction is continued to completion, requiring from aboutone hour and less than seven hours, dependent on the configuration ofthe apparatus, the degree of agitation, and the quantity of alloy to bereacted.

On completion of the reaction, the autoclave and contents are cooled anddischarged, and the tetramethyllead is recovered from the lead andalkali metal chloride components of the reaction mass. When smallportions of hydrocarbon additive are employed in the synthesis reactionthe tetramethyllead is usually accompanied on recovery by saidhydrocarbon liquid.

As already noted, the present invention provides high yields, inaddition to other benefits. To illustrate the general mode of operation,and the results heretofore obtained, a series of base line operationswere conducted, showing generally the procedure already mentioned,except that the only additives or catalysts for the process werehydrocarbon aluminum compounds, and no components having a glycol ethergrouping were provided.

In these operations, in each run, an autoclave was charged with 1,000parts of comminuted monosodium lead alloy, containing weight percentsodium. A mixture of an aluminum type catalyst, dissolved in anhydroustoluene, was then charged, while agitating the contents of theautoclave. The said solution was provided in proportions of about 54parts toluene by weight, and the aluminum catalyst was charged inproportions of about 0.24 weight percent aluminum content based on thealloy charged. According to the identity of the aluminum catalysts, ofcourse, the weight .of the catalyst compound would be varied. Thus, inthe case of using methyl aluminum sesquichloride, (CH Al Cl as thealuminum type catalyst, a typical concentration was about 9.26 parts per1,000 parts of the monosodium lead alloy charged.

The charge thus established was then sealed in the autoclave andpreheated to about C., and then methyl chloride was fed to the autoclaveinterior. The temperature was controlled below about C., and the methylchloride was fed during a period of less than about 30 minutes inproportions corresponding to 1.7 theories, or about 370 parts by weightper 1,000 parts of the alloy charged.

Upon completion of the reaction, after additional reaction for a periodof approximately two hours, the contents of the autoclave were cooledand removed from the interior. The amount of tetramethyllead producedwas determined by its extraction from the reaction mixture, or reactionmass, with a hydrocarbon solvent and by reaction of the tetramethylleadwith iodine of an aliquot of the liquid extract, followed by backtitration. Alternatively, in some instances, the reaction mass wassubjected to steam distillation, for separation of the tetramethylleadfrom the excess lead solids and sodium chloride component of thereaction mass.

A series of operations as above described was carried out, using theprocedure indicated and with occasional slight variation in the amountof catalyst provided. Using triethyl aluminum as the catalyst, theaverage yield in a substantial number of operations obtained was 77.9percent, and when using methyl aluminum sesquichloride as a catalyst .incomparable concentrations, the average yield was 76.8 percent.

The reaction mass attained in the above described base line runs wasquite reactive, in that, when portions were exposed to the atmosphere,considerable turning occurred. The fuming is attributed to the existencein the reaction mass of aluminum hydrocarbon moieties, expressed as AlR.These groups, wherein Al is the monovalent equivalent and R is ahydrocarbon or a hydrogen, are capable of reacting with oxygen andreleasing microscopic particles of aluminum oxide. These particles areso fine that they appear as a fog and tend to foul heat exchangesurfaces in recovery equipment.

To illustrate the operation of the present invention, the followingWorking examples are given.

Example 1 In this operation, the procedure described for the base lineruns was followed, except that the aluminum catalyst, in this casetriethyl aluminum, Was provided in the proportions of 0.46 weightpercent, based on the alloy, and in addition dimethyl ether ofdiethylene glycol was concurrently charged, -in the proportions of aboutmole per mole of the triethyl aluminum. This corresponds to aconcentration of 0.11 Wt. percent aluminum.

Upon completion of the reaction, it was found that a yield of 93 percentof tetramethyllead had been obtained, representing a yield improvementof 15 percent above the results obtained according to the base-lineprocedure. In addition, inspection of the reaction mass produced by theprocess showed that it was not sticky or lumpy, and could be readilydischarged from the autoclave without being significantly air-sensitive,viz., did not exhibit fuming when contacted with air.

In the foregoing example, as indicated, the aluminum catalyst plus thedimethyl ether of diethylene glycol were added at substantially the sametime. In other operations, alternative modes of introducing the pluralcatalyst components have been employed. These include the following:

Reverse addition-the synergist co-catalyst is added and thereafter thealuminum catalyst is provided.

Premixed additionin this operation, the aluminum catalyst, and thesynergist cocatalyst of the present invention, with or Without ahydrocarbon, are mixed together prior to adding to the autoclave charge.

In other instances, the catalyst system, viz., the aluminum alkyl plusthe synergist, are added in delays, or increments spaced apart byseveral minutes, but within the first minutes or one-half hour ofreaction. As is exhibited by the following tabulated examples, thesevarious modes of addition are all quite satisfactory.

To illustrate the scope of the present invention more fully, thefollowing table cites the results obtained in additional workingexamples, wherein the catalyst system included the hydrocarbon aluminumcompound and a dialkyl ether of a lower polyethylene glycol.

the synergestic co-c-atalyst component according to the presentimprovement. A determination was made, for each operation, of thequantity of the reaction mass discharged from an autoclave by mechanicalmeans associated therewith. This study showed that from 68 to 72 percentof the reaction mass was discharged following each run, the averagebeing 71.4 percent.

When the same operations were repeated, but the catalyst included methylaluminum sesquichloride and a loW- er dialkyl ether of a lowerpolyethylene glycol, substantial improvement in the amount of dischargefollowing Aluminum Hydrocarbon Lower Alkyl Ether of Lower ComponentPolyethylene Glycol 'IML Increase Ex. Catalyst Hydrocarbon, Yield, OverB ase Concentration Feed if any Percent Line, Identity Identity Moles/ GIn. Percent Percent of Atom. Al

Alloy (C2H5)sAl 0. 12 Dirlnetliyl other of diethylene 0.5 ReverseToluene 89. G 11.7

g yco (CzI'I5)3A1 0. 11 d 0.75 81. 2 3. 3 (CzH5)3A1 0. 11 0.77 82.8 4. 9(CzHshAiH 0. 105 0. 36 80. 3 11. 4 (CzH5)2AlI'I-i- 0.12 0. 50 90. 3 12.4

2H5)aAl (CHzDaAlzCla 0. 12 0. 69 90. 7 13. 9 (CHslsAlzCls 0. 12 0. 6989. 8 13. O (CHahAlzCls 0. 12 0. 69 90. 6 13. 8 (CHslsAleCls 0. 12 O. 6991. 6 14. 8 (CH3)3A12G13 0. 092 1. 94. 3 17. 5 (CHz)sAlzCla 0. 12 1 0.53 87. 0 l0. 2

g Y (CH3)3A12C13 0. 12 .do 0. 53 90. 1 l3. 3 (CHa)3A.2C1s 0.12 d0 0. 5O79. 4 2. 6 (CH3)3A12C13 0.12 do 1. 50 81. 7 4. 9 (CHa)aAlzCla O. 12Dimethyl ether of tetra- 0.71 88. 5 11.7

ethylene glycol. (CHahAlgCls 0.12 Methyl-ethyl ether of O. 44 88. 8 12.0

diethylene glycol. (OH3)3A12C13 0.12 Dirlnetiiyl ether of ethylene 0. 5186. 4

g yco The foregoing examples illustrate typical excellent resultsobtained according to the present process. In addition to the goodyields obtained, the ease of operability was clearly increased owing tothe fact that the reaction product mixture, or reaction mass is alteredin physical properties. This alteration is evidenced not only by thelower chemical reactivity, on exposure to air, which is attained, butalso is shown by the ease with which the material can be discharged froma reaction zone. Reaction mass includes not only the tetramethylleadengendered by the process, but also the substantial quantity of finelydivided lead particles resultant from the reaction, sodium chlorideobtained as a joint product, and the hydrocarbon liquid when employed.The improvement in processability is shown by the examples below:

Example 19 Seven reactions were carried out according to the standardprocedure already described employing an aluminum hydrocarbon catalystand toluene, but not using each operation was attained. Thus, for thecatalyst system, methyl aluminum sesquichloride-diethyl ether ofdiethylene glycol, the average amount of discharge in four sequentialoperations was 89.5 percent representing a gain in efliciency of over 18percent, the range being from 87 to 91 percent discharged. A similarseries using the catalyst system methyl aluminum sesquichloride and thedimethyl ether of diethylene glycol resulted in an average dischargeefficiency of 83 percent, or an improvementbf about 12.5 percent.Accordingly, the present invention not only results in good yields oftetramethyllead, but aids the discharge of the products of the reactionfrom a reaction zone. Similar benefits are, of course incurred intechniques available for the continuous reaction of sodium lead alloy ormethyl chloride to obtain tetramethyllead.

To illustrate further the beneficial results obtained, with otherexamples of the co-catalysts employed according to the present process,the following examples give the results in an additional series ofoperations.

Aluminum Hydrocarbon Co-Catalyst Component Yield Hydrocarbon IMLIncrease E Catalyst Feed Component, Yield, Over Base ConcentrationMoles/ Gm. ii any Percent ine, Identity A1, Wt. Percent Identity Atom.Al Percent of Alloy (CH3)3A1zCl3 0. 12 Dioxolane 0.32 Normal Toluene 86.3 9. 5 C2 5 s U. 12 d0 (1 d 87. 2 9. 3 (CH3)3(12C13 0. 12 1,4-di0xane80.0 3. 2 (CH3)3AlzC13 0. 12 Dillnetliyl et hylene 96. 5 1S). 7

g yco (OH3)3A12C13 0.12 Diethyl ether of diethylene 93. 5 16. 7

glycol and dioxolanel (CHQQAl Cla 0. 12 Dimethyl ether of ethylene 1. 18Normal do.- 91. 0 14. 2

glycol and dioxolane. 26 (C2H5)3A 1 0.12 Methyl ether of methyl tetra-About 1 Mixed "do 93. 9 About 15 hydrofuran.

1 Used in approximate equal volume ratio. 2 Dioxolane in approximatelypercent volume concentratlon.

In all the foregoing examples, the reaction masses obtained, prior toremoval of the tetramethyllead therefrom, were relatively free-flowing,granular appearing materials. In contrast, in the base-line operationsprevi- As evidenced from the examples above, the yields obtainedgenerally represent a significant improvement over the best yields intetramethyllead synthesis heretofore encountered. Further, it is foundthat these yields are in ously discussed, the reaction mixtures wererelatively excess of mere cumulative yields. Thus, when the disticky andgummy, as shown by the information previmethyl ether of ethylene glycolwas employed in the ously given on the efficiency of discharge. Inaddition, proportions found effective as a co-catalyst (Example in allthe above given examples, the reaction masses did 18) a yield of only 2%was obtained. When the dimethyl not exhibit fuming when exposed to theatmosphere. ether of diethylene glycol was employed, in the presence Toillustrate further additional catalyst combinations of toluene, theyields also encountered were quite low. employed in other embodiments ofthe present invention, The benefits of the process are significant notonly in the the following examples are typical illustrations of catalysthigh yields customarily realized but also in the attainment systems forthe process. When these catalyst systems are of good yields with a greatreduction in the amount of employed, similarly beneficial results areobtained. aluminum type catalyst required.

Ex. Aluminum (Jo-Catalyst Hydrocarbon added,

Component 1t any 27 (10411 3A1 Dirlnetliyl ether of diethylene Aromaticpetroleum cut.

g yco 28 (CaHn) 3A1 Dirlnopyl ether of diethylene None.

ay 29 (CmH2o)sAl Melihyllethyl ether of ethylene Toluene.

g yco 3O (0011mm Dilfutyll ether of diethylene 2,2,4-trimethyl hexane.

g yco (C4H9)gA1H Dihexyl ether of ethylene glycol 1,2-dimethyl benzene.(CaHmAl Ethyl ether of methyl tetra- Propyl benzene.

hydrofuran. (C2H5)aA1 Cyclohexyl ethyl diether of None.

diethylene glycol. (CHmAl Phtlanyllethyl diether of ethylene Toluene.

g yco As additional examples of catalyst components, which can be usedas the second or synergistic catalyst component in place of thosespecially illustrated above, are: cyclohexyl methyl ether of ethyleneglycol, cyclopentyl butyl ether of triethylene glycol, diphenyl ether oftetraethylene glycol, butyl ether of methyl tetrahydrofuran,2-methyl-1,4-dioxane, methyl dioxolaneand others. Additional examples ofcatalyst system components in which are used a plurality of compoundshaving the desired glycol ether grouping, are mixtures of dimethyl etherof ethylene glycol and methyl ethyl ether of diethylene glycol, methylethyl ether of diethylene glycol with dioxolane, and numerous others.

The reasons for the highly beneficial results obtained by the presentprocess are not fully understood. However, it appears that the effectivecatalyst systems are actually new compositions representing complexmaterials between the hydrocarbon aluminum component and the organocomponent having glycol ether type linkages therein. This is evidencedin several ways. Firstly, when a hydrocarbon aluminum component and oneof the cocatalysts involved in the present invention are mixed,extraneous of the reaction system, a homogeneous product usuallyresults. This is particularly marked when the glycol containing materialis provided in proportions of approximately one-half mole per mole ofthe aluminum containing material. However, homogeneous materials areobtained when establishing such admixtures with the glycol materialsvarying in proportions from one-fourth up to four or five moles per gramatom of aluminum in the aluminum component. The absence of fuming uponformation of such complexes, either prior to utilization in the reactionfor synthesizing tetramethyllead, or as evidenced by the attributes ofthe resultant reaction mass, is indicative of the absence ofnon-complexed hydrocarbon aluminum bonds of moieties, in as much asthese latter are well known to be quite reactive with atmosphericoxygen. Accordingly, the catalyst system employed under the presentprocess represents new and novel compositions of matter utilizable forthe indicated process, and also as alkylating agents for reaction withmetal salts, or for convenient sources of hydrocarbon-aluminum moietiesin an easily handled transportable form.

As already shown, the glycol-type linkage containing component can be asingle compound or can be, when desired, two or even more compounds. Infact, in some respects, further benefits are thus realized which areparticularly advantageous in certain environments. Thus, in Example 24,an approximate equal volume mixture of diethyl ether of diethyleneglycol and dioxolane was employed. It is found that the rapidity ofreaction in this instance is improved, particularly as evidenced by thespeed at which a reaction is initiated. Thus, in the case of fouroperations using a catalyst system consisting of methyl aluminumsesquichloride and the diethyl ether of diethylene glycol, the averagetime required before the reaction was proceeding at a realistic rate,after attainment of reaction temperatures, was 53 minutes. In contrast,in three operations wherein the catalyst system included methyl aluminumsesquichloride, and diethyl ether of diethylene glycol in conjunctionwith dioxolane, as in Example 24, the average time required to initiatereaction at a realistic rate was 31 minutes, representing an improvementof approximately 40 percent.

As previously noted, the present invention not only provides appreciableincrease in yield of the maximum yields obtained when using aluminumcatalyst as the sole catalyst component, but in addition the yieldincrease is achieved when using appreciably lower amounts ofaluminum-hydrocarbon catalyst. Thus, although the optimum proportions ofaluminum catalyst heretofore have been, in certain systems, in the rangeof about 0.18-0.22 weight percent of aluminum of the sodium lead alloycharged, the examples given above show a high degree of effectiveness isobtained when using, typically, only half as much aluminum catalyst. Itwill be understood that, although the present invention is permissiveof, and results in, high yields, even with low proportions of thealuminum component, than heretofore believed necessary, that a widerange of aluminum or aluminum compound concentration is permissive.Thus, the benefits of the invention are obtained when proportions ofaluminum of from about 0.04 to about 0.25 weight percent of the alloy,are used. A preferred range is from about 0.08 to 0.15 weight percent.

The relative amount of the components of the catalyst systems are nothighly critical, but are frequently important. Highly eifective resultsare obtained from the low proportions of about one-fourth mole per gramatom of the aluminum in the aluminum-hydrocarbon catalyst component upto as high as five moles per gram atom of aluminum. In particularsystems, the relative proportions are more important. In the case ofalkyl aluminum chloride or trialkyl aluminum combinations with di-loweralkyl ethers of lower polyethylene glycols, an optimum proportion isfound in the range of from one-half to about two moles of the di-loweralkyl ether per atom of aluminum. Thus, in the case of dimethyl ether ofdiethylene glycol with methyl aluminum sesquichloride, a mole ratio of1.35-1 resulted in a yield of 94.3 percent (Example 11), even though thealuminum concentration was less than one-tenth weight percent of thealloy. It was found that ratios above and below this level tended todecrease the yield obtained, although as exhibited by the examples,appreciable increase over the best results obtained solely with analuminum hydrocarbon catalyst were nevertheless realized.

The mode of addition of the catalyst is sometimes important. In the caseof a large number of operations using methyl aluminum sesquichloride inconjunction with the dimethyl ether of diethylene glycol, it was foundthat the yield was not sensitive to the mode of addition. On the otherhand, when methyl aluminum sesquichloride and the diethyl ether ofdiethylene glycol were used together, it was found highly desirable todefer addition of some of the methyl aluminum sesquichloride for severalminutes after a portion thereof, with the diethyl ether of diethyleneglycol, had been introduced to the reaction zone. The preferred mode ofaddition for any explicit catalyst system is readily determinable.

What is claimed is:

l. A catalyst system for the preparation of tetramethyllead compoundsfrom a sodium-lead alloy and an alkyl chloride consisting of methylaluminum sesquichloride and at least one co-catalyst which is an organiccompound consisting of carbon, hydrogen and oxygen, said at least oneco-catalyst being an organic compound having at least one glycol diethertype group and being at least one selected from the class consisting of,

(a) dihydrocarbon ethers of lower polyethylene glycols having from twoto seven glycol groups,

(b) dihydrocarbon ethers of ethylene glycol,

(c) lower alkyl ethers of 1,4-dioxane,

(d) l,4-dioxane,

(e) dioxolane,

(f) lower alkyl dioxolane,

(g) hydrocarbon ethers of methyl tetrahydr-ofuran, and

(h) mixtures thereof,

the hydrocarbon radicals of the said co-catalysts being radicalsselected from the group consisting of alkyl, phenyl, cyclohexyl, andmixtures thereof.

2. A catalyst system for the preparation of tetramethyllead compoundsfrom a sodium-lead alloy and an alkyl chloride consisting of an aluminumcatalyst and at least one co-catalyst which is an organic compoundconsisting of carbon, hydrogen, and oxygen,

(A) said aluminum catalyst being at least one selected from the groupconsisting of,

(1) aluminum,

(2) aluminum trichloride,

(3) aluminum tribromide,

(4) aluminum triiodide,

(5) a hydrocarbon aluminum compound having at least one hydrocarbongroup bonded to aluminum by a carbon-aluminum linkage and being at leastone selected from the grouping consisting of,

(a) trihydrocarbon aluminum compounds, (b) hydrocarbon aluminumchlorides,

(c) hydrocarbon aluminum hydrides,

(d) hydrocarbon aluminum alkoxides, and (e) mixtures thereof, and

- l0 (6) mixtures thereof, wherein said at least one hydrocarbon groupbonded to aluminum is a hydrocarbon group selected from the classconsisting of alkyl, phenyl, and mixtures thereof; and

(B) said at least one co-catalyst being a lower alkyl ether of methyltetrahydrofuran, the alkyl group of said lower alkyl ether having fromone to about 10 carbon atoms.

3. The catalyst system of claim 1 further characterized by said methylaluminum sesquichloride being present in a quantity sufficient toprovide an aluminum concentration of from about 0.04 to 0.25 weightpercent of said sodiumlead alloy.

4. A catalyst system for the preparation of tetramethyllead compoundsfrom a sodium-lead alloy and an alkyl chloride consisting of suflicientmethyl aluminum sesquichloride to provide an aluminum concentration offrom about 0.04 to 0.25 weight percent of said sodium-lead alloy andsuflicient dimethyl ether of diethylene glycol to provide of from about0.25 to 5 moles per atom of aluminum.

5. A catalyst system for the preparation of tetramethyllead compoundsfrom a sodium-lead alloy and an alkyl chloride consisting of suflicientmethyl aluminum sesquichloride to provide an aluminum concentration offrom about 0.04 to 0.25 weight percent of said sodium-lead alloy andsufiicient diethyl ether of diethylene glycol to provide of from about0.25 to 5 moles per atom of aluminum.

6. A catalyst system for the preparation of tetramethyllead compoundsfrom a sodium-lead alloy and an alkyl chloride consisting of sufiicientmethyl aluminum sesquichloride to provide an aluminum concentration offrom about 0.04 to 0.25 weight percent of said sodium-lead alloy andsufiicient methyl ethyl ether of diethylene glycol to provide of fromabout 0.25 to 5 moles per atom of aluminum.

7. A catalyst system for the preparation of tetramethyllead compoundsfrom a sodium-lead alloy and an alkyl chloride consisting of sufiicientmethyl aluminum sesquichloride to provide an aluminum concentration offrom about 0.04 to 0.25 weight percent of said sodium-lead alloy andsufiicient of a mixture of dimethyl ether of ethylene glycol anddioxolane to provide of from about 0.25 to 5 moles of said mixture peratom of aluminum.

8. A catalyst system for the preparation of tetramethyllead compoundsfrom a sodium-lead alloy and an alkyl chloride consisting of sufiicientmethyl aluminum sesquichloride to provide an aluminum concentration offrom about 0.04 to 0.25 weight percent of said sodium-lead alloy andsufficient of a mixture of diethyl ether of diethylene glycol anddioxolane to provide of from about 0.25 to 5 moles of said mixture peratom of aluminum.

9. A catalyst system for the preparation of tetramethyllead compoundsfrom a sodium-lead alloy and an alkyl chloride consisting of sufiicientmethyl aluminum sesquichloride to provide an aluminum concentration offrom about 0.04 to 0.25 weight percent of said sodium-lead alloy andsufficient 1,4-dioxane to provide of from about 0.25 to 5 moles per atomof aluminum.

10. A catalyst system for the preparation of tetramethyllead compoundsfrom a sodium-lead alloy and an alkyl chloride consisting of sufiicientmethyl aluminum sesquichloride to provide an aluminum concentration offrom about 0.04 to 0.25 weight percent of said sodium-lead alloy andsufiicient dimethyl ether of ethylene glycol to provide of from about0.25 to 5 moles per atom of aluminum.

11. A catalyst system for the preparation of tetramethyllead compoundsfrom a sodium-lead alloy and an alkyl chloride consisting of (A) atleast one alkyl aluminum compound selected from the group consisting of,(1) aluminum trialkyls, (2) alkyl aluminum chlorides,

1 1 (3) alkyl aluminum hydrides, and (4) alkyl aluminum alkoxides; and

(B) a lower alkyl ether of methyl tetrahydrofuran,

' each alkyl group of the foregoing Items A and B having from one toabout ten carbon atoms.

12. A catalyst system for the preparation of tetramethyllead compoundsfrom a sodium-lead alloy and an alkyl chloride consisting of sufficienttriethyl aluminum to provide an aluminum concentration of from about0.04 to 0.25 weight percent of said sodium-lead alloy and suflicientmethyl ether of methyl tetrahydrofuran to provide of irom about 0.Z to 5moles per atom of aluminum.

References Cited UNITED Examiners.

J. G. LEVITT, L. G. XIARHOS, Assistant Examiners.

1. A CATALYST SYSTEM FOR THE PREPARATION OF TETRAMETHYLLEAD COMPOUNDSFROM A SODIUM-LEAD ALLOY AND AN ALKYL CHLORIDE CONSISTING OFMETHYLALUMMINUM SESQUICHLORIDE AND AT LEAST ONE CO-CATALYST WHICH IS ANORGANIC COMPOUND CONSISTING OF CARBON, HYDROGEN AND OXYGEN, SAID ATLEAST ONE CO-CATALYST BEING AN ORGANIC COMPOUND HAVING AT LEAST ONEGLYCOL DIETHER TYPE GROUP AND BEING AT LEAST ONE SELECTED FROM THE CLASSCONSISTING OF, (A) DIHYDROCARBON ETHERS OF LOWER POLYETHYLENE GLYCOLSHAVING FROM TWO TO SEVEN GLYCOL GROUPS, (B) DIHYDROCARBN ETHERS OFETHYLENE GLYCOL, (C) LOWER ALKYL ETHERS OF 1,4-DIOXANE, (D) 1,4-DIOXANE,(E) DIOXOLANE, (F) LOWER ALKYL DIOXOLANE, (G) HYDROCARBON ETHERS OFMETHYL TETRAHYDROFURAN, AND (H) MIXTURES THEREOF, THE HYDROCARBONRADICALS OF THE SAID-CO-CATALYSTS BEING RADICALS SELECTED FROM THE GROUPCONSISTING OF ALKYL, PHENYL, CYCLOHEXYL, AND MIXTURES THEREOF.